Thanks for the exposee. I agree with all most all of your conclusions. I hope you don't mind if I critique a few side points a bit.

Jumping to my summary conclusion (for time conscious readers...)

I think that the gullies are created by dust flows, and that their distribution is dependant on wind regimes.

The chart you show of temperatures is very excellent. One might conclude that the latitudinal region of high temperature gradient is where high winds would be found that could mobilize more dust and sand. One also needs to think about where these materials would settle out.

The one part of your essay I didn't like was having to call in orbital eccentricity to explain gullying in the more temperate regions. It seems to me that these temperate dark streaks (+/- gullies) are only a few years old, not tens of thousands. The last big dust storm would have covered them up, wouldn't it? I also have a question about "bleaching"; would mineral grains really bleach under UV? The current rover dust was shown to be almost pure iron. While I don't know for sure, I would guess that iron does not appreciably bleach with UV. Those sun grazing iron nickel meteorites don't look very bleached. Thus, I believe that the temperate gullies are occasionally active currently, and apparently, CO2 frosts or blankets are not involved.

The thaw period of the CO2 would be a likely time for flows to be triggered near the poles. But what of the temperate flows?

My proposed explanation is "dust cycling". Dust is blown around the whole planet, but the really fine dust takes much longer, and very still air to settle out. This still air would occur in the downdraft zones over the cold, north facing slopes of the temperate region . This fine dust would be more prone to flow, and trigger avalanches of larger particles. It could even be picked up from the fan aprons, and redistributed in the next dust storm. The equatorial region would lack gullies because either the local temperature differentials are not high enough to have downdrafts, or the wind velocity is too high for the fine dust to settle out extensively. The polar region, totally lacking temperature differentials (especially in winter), would have very still air that allows the fine dust to settle out near the margins of the ice pack, or even freeze out with the CO2 ice, acting as nuclei.

The Malin picture M09-05128 in your essay showed what looked to be like two flows that had crossed each other at a high angle. This would be pretty convincing evidence of avalanching, non liquid flow. This was near the lower part of the picture.